04:27 05-01-2026

How a 120 Ah battery retrofit transformed a BMW i3's range

Discover how a BMW i3 owner upgraded to a 120 Ah battery, boosting range to 525 km. Costs, certified retrofit details, and highway results at 120 km/h.

BMW i3 owner Herve shows how electric cars can reset expectations about a vehicle’s lifespan. His philosophy is simple: squeeze out maximum efficiency without giving up comfort. At home that means solar panels, a heat pump, and a smart electricity plan; in the garage, the i3 he chose back in 2016 after trying the version with a small gasoline generator (Rex).

Over time, he didn’t crave a new car so much as more range from the one he already knew well. The target was a 120 Ah battery, lifting capacity from roughly 33 to about 42 kWh. In France such a retrofit isn’t officially encouraged, but the insurer had no objections if a genuine, certified BMW pack was used. The next step was finding the right specialists: options in Germany and the Czech Republic were on the table, and the latter offered a more flexible approach with software recalibration and installation of a certified battery with prior mileage.

The budget was planned like a serious project. A pack with 99% state of health (around 15,000 km of use) plus labor came to about €8,500. Then Herve sold his original battery for €2,500 to the owner of an early i3 60 Ah, cutting the effective cost to roughly €7,500. For an upgrade that extends a car he already trusts, that looks like money spent with a clear purpose.

The result speaks for itself: combined range (battery plus Rex) rose from roughly 400 to about 525 km. On the highway at 120 km/h, the i3 now covers around 350 km instead of the previous 280. It’s the same compact city car, only with endurance that makes long stretches less of a compromise and daily charging routines easier to plan.